Load reduction

ABSTRACT

A method and apparatus are disclosed for selectively providing a fluid communication path between a plunger element and a contact region of an intermediate element that drives the plunger element. The fluid communication path is suitable for lubricant flow to enable a contact zone to occasionally be lubricated. The apparatus includes an elongate plunger element comprising a first end region, an intermediate element comprising a contact region arranged to selectively abut with and thereby urge a further end region of the plunger element and a spring seat member at the further end region of the plunger element. The spring seat member biases the further end region of the plunger element away from the intermediate element during a portion of a cycle of motion of the plunger element. A fluid communication path is thereby provided between an abutment surface of the further end region and the contact region.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national stage application under 35 U.S.C. 371 ofPCT Application No. PCT/EP2013/058358 having an international filingdate of 23 Apr. 2013, which designated the United States, which PCTapplication claimed the benefit of European Patent Application No.12166665.5 filed on 3 May 2012, the entire disclosure of each of whichare hereby incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a method and apparatus for selectivelyproviding a fluid communication path that allows lubricant to flow to adesired location in between two moving parts. In particular, but notexclusively, the present invention relates to a plunger and tappetarrangement. A resilient spring seat is used to separate the plunger andtappet by a short distance at a particular point of a cycle of theplunger movement. The momentary separation allows lubricant to flow froma surrounding region into the space created between the plunger andtappet.

BACKGROUND OF THE INVENTION

In known pump assemblies an intermediate element, often referred to asan intermediate drive member, and often in the form of a tappet,transmits drive from a cam mechanism to a pumping plunger. The pumpingplunger is used to pressurise fluid in a pumping chamber for delivery toa desired location. For example, the fluid could be engine fuel of adiesel engine fuel injection system.

Tappets are used to reduce lateral forces applied to a pumping plungerso that in general the pumping plunger is driven in a reciprocal motionby the tappet backwards and forwards along a respective longitudinalaxis of motion. Tappets are well known and are generally cup-shapedelements with a cylindrical side wall and solid base. Vents can beprovided in the side wall and/or base of the tappet so that alubricating fluid can flow from around the cam mechanism to regionswithin the tappet. This helps ensure hydraulic forces do not inhibitfree movement of the tappet within a tappet bore in a housing. Thus,pumps which can operate at high pressures, employ a reciprocatingplunger to do work on the fluid being pumped. The plunger is movedforward during a pumping stroke by applying a load mechanically to anopposite end of the plunger via a tappet. On a return stroke of thecycle of motion of the plunger, the plunger is held against the tappetby a spring referred to as a return spring.

During the pumping stroke of the cycle the contact load between tappetand plunger can be very high with small lateral forces leading tolubrication breakdown and fretting wear at the contact zone. The factthat the surfaces of prior art systems are continually held togetherprevents the flow of lubrication into the contact zone between an end ofthe plunger and a contact region of the tappet. This allows wear debristo be retained and this can further abrade the juxtaposed surfaces overtime. Patent application DE102010041002 discloses an apparatus as set inthe preamble of claim 1.

It is an aim of the present invention to at least partly mitigate theabove-mentioned problems.

It is an aim of the certain embodiments of the present invention toprovide a method and apparatus that from time-to-time provides a fluidcommunication path, of the type along which lubricant can flow, betweena plunger element and a contact region of an intermediate element.

It is an aim of certain embodiments of the present invention to bias aplunger away from a tappet at least momentarily at a point in time ormore than one point in time during a cycle of motion of the plunger.

It is an aim of certain embodiments of the present invention to providea pump assembly in which lubricant can selectively flow between acontact region of an intermediate element such as a tappet and an end ofa plunger element so that fretting and wear rate can be reduced betweenjuxtaposed surfaces on the component parts.

It is an aim of certain embodiments of the present invention to reducefretting and wear rates in a pump assembly by allowing a contact area tobe flushed with fresh lubricant before each load cycle.

It is an aim of certain embodiments of the present invention toselectively cause a small gap to be opened between component parts in apump assembly when the component parts are unloaded.

It is an aim of certain embodiments of the present invention to providea squeeze film between opposed surfaces of a plunger element andintermediate element in a pump assembly.

It is an aim of certain embodiments of the present invention to providea method of lubricating between a plunger element of a pump assembly andan intermediate element providing drive to the plunger element.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is providedapparatus for selectively providing a fluid communication path between aplunger element and a contact region of an intermediate element thatdrives the plunger element, comprising:

-   -   an elongate plunger element comprising a first end region; an        intermediate element comprising a contact region arranged to        selectively abut with and thereby urge a further end region of        the plunger element; and a spring seat member at said further        end region that biases the further end region away from the        intermediate element during a portion of a cycle of motion of        the plunger element to thereby provide a fluid communication        path between an abutment surface of said further end region and        said contact region.

Aptly, the intermediate element comprises a tappet received forreciprocating sliding motion in a housing bore of a pump housing of apump assembly.

Aptly, the tappet comprises at least one through-hole in a cylindricalside wall and/or base wall thereof, said through-hole providing a fluidpath portion connected to said fluid communication path.

Aptly, the fluid communication path provides lubricating fluid betweensaid abutment surface and said contact region at an end of a returncycle of the plunger element.

Aptly, the first end region of said plunger element is locatable into ablind end of a pump bore of a pump head of a pump assembly; and theintermediate element further comprises a drive surface that is driveableby a cam or cam rider element of the pump assembly to thereby urge saidcontact region against said abutment surface.

Aptly, the apparatus further comprises a return spring member that urgesa surface of the spring seat element away from a pump head of a pumpassembly.

Aptly, the spring seat member and the plunger element are integrallyformed or the spring seat member is secured to said plunger element formovement therewith.

According to a second aspect of the present invention, there is provideda pump assembly comprising:

-   -   a pump housing comprising an axially extending opening and at        least one housing bore extending generally radially from said        opening;    -   at least one intermediate element each received for        reciprocating sliding motion in a respective housing bore and        comprising an internal chamber region;    -   at least one pump head comprising a pump bore having a blind end        and secured to said pump housing;    -   an elongate plunger element in each chamber region driveable in        use via a respective intermediate element, and comprising a        first end region that pressurises fluid in a pumping chamber        provided by a respective pump bore, and a further end region;    -   a cam and/or cam rider element in said axially extending opening        having an inner surface co-operable with a cam driveshaft and an        outer surface co-operable with a drive surface of said        intermediate member; and    -   at least one spring seat member each at a further end region of        a respective plunger element that biases the further end region        away from a contact region of the intermediate element during a        portion of a cycle of motion of the plunger element to thereby        provide a fluid communication path between an abutment surface        of the further end region and said contact region.

Aptly, the spring seat member and said plunger element are integrallyformed or the spring seat member is secured to said plunger element formovement therewith.

According to a third aspect of the present invention there is provided amethod of lubricating between a plunger element of a pump assembly andan intermediate element providing drive to the plunger element, themethod comprising the steps of:

-   -   driving a first end region of a plunger element in a first        reciprocating motion with respect to a blind end of a pump bore        of a pump head by selectively urging a contact region of an        intermediate element proximate to a further end region of the        plunger element in a further reciprocating motion;    -   via a spring seat member at the further end region of the        plunger element, biasing the plunger element away from the        intermediate element during a portion of a cycle of motion of        the plunger element; and    -   providing lubricating fluid between an abutment surface of said        the further end region and said contact region as the further        end region is biased away from the intermediate element.

Aptly, the method further comprises cooling and removing debris frombetween the abutment surface and said contact region via the lubricatingfluid.

Aptly, the method further comprises providing a squeeze film layerbetween the abutment surface and said contact region via the lubricatingfluid.

Aptly, the method further comprises opening and closing a gap betweensaid abutment surface and said contact region each cycle of the plungerelement.

Aptly, the portion of a cycle comprises an end of a return cycle of theplunger element in which the fluid in the pump bore expands and saidfirst reciprocating motion further comprises a pump cycle portion inwhich fluid in the pump bore is compressed.

Aptly, the method further comprises biasing the further end region via aspring seat member integrally formed with said plunger element or via aspring seat member secured to said plunger element for movementtherewith.

Certain embodiments of the present invention provide the advantage thata fluid communication path between an end of a plunger and contactregion of an intermediate element such as a tappet is provided. Thisallows lubricant to be drawn into the region between opposed faces andto cool, lubricate and wash away debris. This also provides a squeezefilm between the opposed faces as they close back together so that thefaces are kept apart for a longer period than would otherwise be allowedwith prior known systems. This longer period reduces the wear created bydrive motion and/or the inevitable lateral motion induced as part of thereciprocating pumping motion.

Certain embodiments of the present invention provide a method forreducing fretting and wear and for removing debris in a high pressurehead of a pump assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described hereinafter,by way of example only, with reference to the accompanying drawings inwhich:

FIG. 1 illustrates a pump assembly;

FIG. 2 illustrates a pump head, return spring and tappet;

FIG. 3 illustrates another view of the pump head, return spring andtappet;

FIG. 4 illustrates a plunger end in an internal chamber of the tappet;and

FIG. 5 illustrates the features shown in FIG. 4 and a spring seatmember.

In the drawings like reference numerals refer to like parts.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a pump assembly 100. The pump assembly includes amain pump housing 101 provided with an axially extending opening 102.The opening extends in the direction into the page shown in FIG. 1. Acam shaft (not shown) having an axis of rotation 103 drives aneccentrically mounted cam 104 mounted in the opening.

The main pump housing 101 is provided with a first, second and thirdradially extending opening or through bore 105 a, 105 b, 105 c, each ofwhich communicates at a radially inner end thereof with the axiallyextending opening 102 which extends through the housing. Other numbersof through bores can of course be utilised according to certain otherembodiments of the present invention. A radially outer end of eachhousing bore 105 a, 105 b, 105 c receives a respective pump head 110 a,110 b, 110 c. Each pump head is substantially identical and thereforereference will be made hereinafter only to the upper pump head 110 ashown in FIG. 1 which is described and shown in the further drawings.

FIG. 2 illustrates parts of the pump head 110 a in more detail. The pumphead includes a head portion 200 which is a substantially rectangularbody. A substantially cylindrical central region extends downwardly froman underside region 201 of the pump head. The cylindrical extension 202encompasses a substantially cylindrical pump bore region 203. The pumpbore 203 has a blind end 204 where at least one valve 205 is located.The pump bore 203 also has an open end 206 which thus provides an openmouth of the extension of the pump head. The bore 203 provides a pumpingchamber with the space of the pumping chamber being defined by the blindend 204 of the bore and a first end 210 of a plunger 211. The plunger isan elongate shaft-like member which slides backwards and forwards withinthe cylindrical bore 203 in the pump head. As an upper end surface 212of the first end 210 of the plunger moves upwardly in the directionshown by arrow A in FIG. 2 the volume of the pumping chamber reduces.Equally, as the plunger moves in the direction along the axis ofmovement opposite to the direction shown by arrow A in FIG. 2, thevolume of the pumping chamber increases.

A substantially circular cut out region 215 is provided centrally on thelower surface of the pump head. This is utilised to locate and secure afirst end 220 of a return spring 221. The return spring holds the tappetaway from the pump head in its relaxed state and is compressed as thetappet is urged towards the pump head during a pump stroke part of acycle. The space 215 under the pump head also provides clearance for anupper circular surface 230 of a cup-like tappet 231. The blind end ofthe plunger bore thus defines together with an outer end face of theplunger a pump chamber into which fuel at relatively low pressure may bedelivered and within which pressurisation of fuel to a relatively highlevel suitable for injection takes place as the plunger is driven toperform a pumping stroke upon rotation of the cam or a rider located onthe cam.

The tappet 231 is a substantially hollow body having a cylindrical sidewall 232 which extends from the circumferential region of asubstantially circular base 233. The base and side wall are integrallyformed. The lip of the side wall 232 forms the circular surface which isurged upwards towards the pump head during pumping. The base 233provides a blind end of an internal chamber 240 defined within thetappet. One or more through holes 250 are formed circumferentiallyaround the side wall of the tappet to enable fluid to flow from an outerregion surrounding the tappet body to an inner region within the chamber240. The through holes may be circular or church window style or thelike.

A spring seat 260 is located at a further end 261 of the plunger 211.The spring seat 260 shown in FIG. 2 is secured to the end of the plungerby an interference fit, although it will be appreciated that the springseat could alternatively be integrally formed with the shaft-likeplunger body or could be secured thereto via other ways. The spring seatand plunger move together as one unit. An upper surface 262 of thespring seat seats a further lower end 263 of the return spring.

As illustrated in FIG. 1, the drive shaft co-operates with the cam 104and as shown in FIG. 1 an optional and co-operable generally tubular camrider which extends coaxially with the cam. On the outer surface the camrider is provided with a first, second and third flattened surfacereferred to as flats. Each one of the flats co-operates with the basesurface of a tappet 231 for a respective one of the plungers. As atappet is operably coupled to a plunger, rotation of the shaft causesthe cam rider to ride over the surface of the cam thereby impartingdrive to both the tappet and the plunger. As the tappet 231 is driven adegree of lateral sliding movement is permitted between the lowersurface 270 of the tappet base and the flat of the rider. Optionally, aslipper face may be provided for promoting such sliding movement. Alubricating fluid, such as fuel or the like, is provided in the opening102 of the housing and bore 105 in which the tappet slides to limit weardue to friction.

As the cam is driven, the tappet is caused to reciprocate in the opening105 and the plunger is caused to reciprocate within the plunger bore203. There is thus a first reciprocating motion of the tappet within thehousing bore and a further reciprocating motion of the plunger withinthe pump bore.

The tappet and the pumping plunger are thus driven together causing theplunger to perform a pumping cycle including a pumping stroke duringwhich the tappet and the plunger are driven radially outward from thecentral cam shaft (i.e. towards the respective pump head) which reducesthe volume within the pump chamber 203. During this pumping stroke thepumping plunger is driven inwardly within its plunger bore and fuelwithin the pump chamber is pressurised to a high level. During asubsequent plunger return stroke the tappet and plunger are urged in aradially inward direction, i.e. towards the centre of the housing andaway from the pump head. This return motion is caused by virtue of theresilient nature of the return spring which thus biases the tappet awayfrom the pump head. During the return stroke of the plunger and itsrespective tappet the plunger is urged outwardly from the plunger boreand fuel at relatively low pressure may be allowed to fill theassociated pump chamber via a valve.

The provision of the plunger return spring thus serves to urge theplunger to perform its return stroke and additionally ensures contact ismaintained between the tappet and the flat of the cam rider during thepumping cycle. The tappet and plunger perform cyclic sinusoidal motionand are driven at a desired frequency. Aptly, the maximum frequency isabout around 130 Hz. Aptly, the maximum frequency is about around 120Hz. The tappet has a range of travel between bottom-dead-centre andtop-dead-centre. Aptly, the range of travel is about around 15 mm orless. Aptly, the range of travel is about around 10 mm or less. Thetappet acts as an intermediate element between the cam and/or cam riderelement which provides drive and the plunger which is driven in areciprocal fashion within the pump bore provided by the pump head.

FIG. 3 illustrates the pump head, tappet and return spring shown in FIG.2 in more detail. In particular, FIG. 3 helps clarify how church windowstyle openings 250 are formed at a radially innermost end region of thetappet. Four openings are shown in FIG. 3, although it will beappreciated that other shapes and numbers of openings are possibleaccording to certain other embodiments of the present invention. Theopenings are formed by cut out regions 300 from the cylindrical sidewall and base of the tappet. FIG. 3 also helps illustrate how the pumphead is substantially rectangular in shape, although it will beappreciated that other shapes and configurations are possible accordingto certain other embodiments of the present invention. The pump head maybe secured to the pump housing 101 via bolts or other such securingmechanisms which, in use, extend through the apertures 301 in the pumphead. As illustrated in FIG. 3, the tappet thus provides an internalchamber which encompasses an end of the return spring. The other end ofthe return spring is secured at an upper end thereof to the pump head110.

FIG. 4 illustrates how a plunger extends through the open end 206 of thepump bore into a chamber 240 defined within the tappet. A lower end ofthe plunger 211 has a generally circular abutment surface end 400. Thisabuts with a central contact region 401 on an upper facing surface 402of the base of the tappet. As illustrated in FIG. 4 the central contactregion 401 may be slightly raised with respect to a surrounding regionof the upper surface 402 of the base of the tappet.

A spring seat 260 is a substantially circular, ring-like body formed ofa resilient material. Aptly, the spring seat is formed of hardenedsteel. The cross-section of the spring seat is formed of a radiallyoutermost (with respect to the axis of the plunger) leg 403 which has alower annular contact surface 404 which sits on the upper surface 404 ofthe base of the tappet. The contact point 405 between the spring seatand base of the tappet thus constrains motion of the spring seat in adirection shown by arrow B in FIG. 4. The remaining body of the springseat is generally disc-like with a concave profile on its underside. Theconcave, partially teardrop shaped recess on the lower side of thespring seat helps allow the spring seat to flex. The upper surface 262of the spring seat has an upper annular rib 410 extending as a ringshaped protuberance.

As illustrated in FIG. 4, a small gap 420 can be opened between the endsurface 400 of the plunger and the contact region 401 of the base of thetappet. This space 420 provides a short separation between componentparts. During a pumping process in which a cam rider is urged againstthe lower surface 270 of the tappet, the tappet is pushed against theend of the plunger and the force overcomes the resilient nature of thespring seat. The plunger and tappet are thus effectively locatedtogether for movement as a unitary piece. The pumping stroke follows asthe cam rider drives the tappet and plunger in a direction opposite tothe arrow B shown in FIG. 4 during which the tappet and plunger move asone. At the end of the pumping cycle, the cam rider ceases to urge thetappet (and thus the plunger) in the direction opposite to arrow B. Thereturn spring 221 which acts on the upper surface of the spring seatwhich is urged against the base of the tappet and which carries theplunger with it, then causes motion of the tappet and plunger in thedirection of arrow B. At an end of the return stroke, the resilientnature of the spring seat and the fact that it stands on the base of thetappet causes the plunger end to momentarily be pulled away from thecontact region 401 at the base of the tappet. This separating motioncreates the gap 420 that provides a fluid communication path between thezone between the component parts. The fluid communication path alsocommunicates with the chamber 240 within the tappet and, via the ventsin the tappet 250, the surrounding regions.

FIG. 5 helps illustrate the cylindrical nature of the tappet andcircular disc-like nature of the spring seat in more detail. As shown inFIG. 5, the tappet 231 is a cup-like element having a cylindrical sidewall extending from a substantially circular base. An upper lip 230 ofthe cylindrical side wall of the tappet provides an open mouth to thetappet and the lip 230 may be urged upwardly towards the pump head intoa recess 500 in the central circular inset region 215 on the undersideof the pump head body 200. FIG. 5 also helps illustrate how a raisedcentral region of the upper surface of the base of the tappet may beraised to provide an island 501 which includes a contact surface 401 ofthe tappet at its upper surface.

The upper surface 262 of the spring seat provides an outermostsubstantially flat ring surface 505 which then extends upwardly via anupwardly extending region 506 into the upwardly facing rib region 410.This helps locate/seat the end of the return spring. From the rib movingradially inwards towards the plunger, the upper surface of the springseat then drops into a first concave region 510 separated from an innerconcave region 511 by a convex region 512. The radially innermostcentral region of the spring seat provides a contact region to enablethe spring seat to be secured via an interference fit or the like to theend 261 of the plunger. It will be appreciated that the plunger body andspring seat could optionally be integrally formed.

According to certain embodiments of the present invention, a springfeature is thus added between a plunger and tappet or similar component.This causes a small gap to be opened between the component parts whenunloaded. The opening of the small gap operates to draw lubricant intothe gap between the faces. This enables the faces to be cooled,lubricated and cleared of debris. The flow of lubricant into the contactregion also provides a squeeze film to be provided. This squeeze filmhelps keep the opposed faces apart for a longer period than wouldotherwise be possible with prior known systems. This helps reduce thewear created by motion.

The spring effect may be provided by a resilient spring seat asdescribed hereinabove. Alternatively, the biasing effect whichmomentarily moves the parts apart may be achieved in a variety of otherways. For example, a solid spring seat could comprise a ring annulushousing a resilient ‘o’ ring.

Throughout the description and claims of this specification, the words“comprise” and “contain” and variations of them mean “including but notlimited to” and they are not intended to (and do not) exclude othermoieties, additives, components, integers or steps. Throughout thedescription and claims of this specification, the singular encompassesthe plural unless the context otherwise requires. In particular, wherethe indefinite article is used, the specification is to be understood ascontemplating plurality as well as singularity, unless the contextrequires otherwise.

Features, integers, characteristics or groups described in conjunctionwith a particular aspect, embodiment or example of the invention are tobe understood to be applicable to any other aspect, embodiment orexample described herein unless incompatible therewith. All of thefeatures disclosed in this specification (including any accompanyingclaims, abstract and drawings), and/or all of the steps of any method orprocess so disclosed, may be combined in any combination, exceptcombinations where at least some of the features and/or steps aremutually exclusive. The invention is not restricted to any details ofany foregoing embodiments. The invention extends to any novel one, ornovel combination, of the features disclosed in this specification(including any accompanying claims, abstract and drawings), or to anynovel one, or any novel combination, of the steps of any method orprocess so disclosed.

The reader's attention is directed to all papers and documents which arefiled concurrently with or previous to this specification in connectionwith this application and which are open to public inspection with thisspecification, and the contents of all such papers and documents areincorporated herein by reference.

1. Apparatus for selectively providing a fluid communication pathbetween a plunger element and a contact region of an intermediateelement that drives the plunger element, comprising: an elongate plungerelement comprising a first end region; an intermediate elementcomprising a contact region arranged to selectively abut with andthereby urge a further end region of the plunger element; characterizedin that the apparatus further comprises a resilient spring seat memberenabled to flex and arranged at said further end region that biases thefurther end region away from the intermediate element during a portionof a cycle of motion of the plunger element to thereby provides a fluidcommunication path between an abutment surface of said further endregion and said contact region.
 2. The apparatus as claimed in claim 1,wherein: the intermediate element comprises a tappet received forreciprocating sliding motion in a housing bore of a pump housing of apump assembly.
 3. The apparatus as claimed in claim 2, wherein: thetappet comprises at least one through-hole in a cylindrical side walland/or base wall thereof, said through-hole providing a fluid pathportion connected to said fluid communication path.
 4. The apparatus asclaimed in claim 1, wherein: the fluid communication path provideslubricating fluid between said abutment surface and said contact regionat an end of a return cycle of the plunger element.
 5. The apparatus asclaimed in claim 1, wherein: the first end region of said plungerelement is locatable into a blind end of a pump bore of a pump head of apump assembly; and the intermediate element further comprises a drivesurface that is driveable by a cam or cam rider element of the pumpassembly to thereby urge said contact region against said abutmentsurface.
 6. The apparatus as claimed in claim 1, further comprising: areturn spring member that urges a surface of the spring seat elementaway from a pump head of a pump assembly.
 7. The apparatus as claimed inclaim 1 wherein said spring seat member and said plunger element areintegrally formed or the spring seat member is secured to said plungerelement for movement therewith.
 8. A pump assembly comprising: a pumphousing having an axially extending opening and at least one housingbore extending generally radially from said opening; at least one pumphead comprising a pump bore having a blind end and secured to said pumphousing; a cam and/or cam rider element in said axially extendingopening having an inner surface co-operable with a cam driveshaft and anouter surface co-operable with a drive surface of said intermediatemember; and at least one apparatus as set in claim
 1. 9. A method oflubricating between a plunger element of a pump assembly and anintermediate element providing drive to the plunger element, the methodcomprising the steps of: driving a first end region of a plunger elementin a first reciprocating motion with respect to a blind end of a pumpbore of a pump head by selectively urging a contact region of anintermediate element proximate to a further end region of the plungerelement in a further reciprocating motion; via a spring seat member atthe further end region of the plunger element, biasing the plungerelement away from the intermediate element during a portion of a cycleof motion of the plunger element; and providing lubricating fluidbetween an abutment surface of said the further end region and saidcontact region as the further end region is biased away from theintermediate element.
 10. The method as claimed in claim 9, furthercomprising: cooling and removing debris from between the abutmentsurface and said contact region via the lubricating fluid.
 11. Themethod as claimed in claim 9, further comprising: providing a squeezefilm layer between the abutment surface and said contact region via thelubricating fluid.
 12. The method as claimed in claim 9, furthercomprising: opening and closing a gap between said abutment surface andsaid contact region each cycle of the plunger element.
 13. The method asclaimed in claim 9, wherein: said portion of a cycle comprises an end ofa return cycle of the plunger element in which fluid in the pump boreexpands and said first reciprocating motion further comprises a pumpcycle portion in which fluid in the pump bore is compressed.
 14. Themethod as claimed in claim 9, further comprising: biasing the furtherend region via a spring seat member integrally formed with said plungerelement or via a spring seat member secured to said plunger element formovement therewith.